US4021321A - Electrolytic preparation of phosphorous acid from elemental phosphorus - Google Patents

Electrolytic preparation of phosphorous acid from elemental phosphorus Download PDF

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US4021321A
US4021321A US05/640,671 US64067175A US4021321A US 4021321 A US4021321 A US 4021321A US 64067175 A US64067175 A US 64067175A US 4021321 A US4021321 A US 4021321A
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phosphorus
phosphorous acid
halogen
hydrogen halide
aqueous solvent
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Donald A. White
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Monsanto Co
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Monsanto Co
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Priority to GB52017/76A priority patent/GB1527550A/en
Priority to FR7637670A priority patent/FR2335619A1/fr
Priority to IT30404/76A priority patent/IT1065412B/it
Priority to JP51149491A priority patent/JPS5913597B2/ja
Priority to CA267,785A priority patent/CA1089406A/en
Priority to DE19762656593 priority patent/DE2656593A1/de
Priority to BE173283A priority patent/BE849433A/xx
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/22—Inorganic acids

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  • This invention relates to an improved process for the indirect electrolytic oxidation of elemental phosphorus to phosphorous acid, (HO) 2 HPO.
  • Phosphorous acid is available commercially as 30 percent and 70 percent aqueous solutions.
  • the conventional method of preparation of phosphorous acid comprises hydrolyzing phosphorus trichloride according to the diagrammatically simplified reaction:
  • a further advantage of the present invention is the ready availability of the essential reactants.
  • the essential reactants are elemental phosphorus, hydrogen halide (which is reusable), water, and electric current.
  • the possibility of undesirable side reactions occurring is significantly reduced by conducting the electrolysis in an electrolysis medium containing in addition to elemental phosphorus and an aqueous solution of hydrogen halide, a non-aqueous solvent capable of dissolving the molecular halogen generated during the electrolysis as well as at least sufficient amounts of the elemental phosphorus to permit the oxidative reaction between it and the molecular halogen to proceed at a reasonable rate.
  • additional elemental phosphorus dissolves, thereby maintaining a continuous supply of dissolved elemental phosphorus available for reaction so long as some undissolved elemental phosphorus remains.
  • FIG. 1 is a schematic diagram of a cross section of an undivided electrolysis cell suitable for batch operation of the present invention.
  • FIG. 2 is a schematic illustration of a typical flow diagram of a process suitable for continuous operation of the present invention.
  • phosphorous acid can be prepared by the indirect electrolytic oxidation of elemental phosphorous by conducting the electrolysis in an electrolysis medium containing elemental phosphorus, an aqueous solution by hydrogen halide, and a non-aqueous solvent capable of dissolving the molecular halogen generated during the electrolysis as well as at least sufficient amounts of the elemental phosphorus to permit the oxidative reaction between it and the molecular halogen to proceed at a reasonable rate.
  • reaction (6) the net effect of reactions (2) through (5) of the present process are summarized as shown in reaction (6).
  • Electrolytic reduction of hydrogen ions (protons) at the cathode completes the electrochemical reaction.
  • the indirect electrolytic oxidation reaction is carried out by conducting the electrolysis in an electrolysis medium containing elemental phosphorus, an aqueous solution of hydrogen halide, and a non-aqueous solvent capable of dissolving the molecular halogen generated during the electrolysis as well as at least sufficient amounts of the elemental phosphorus to permit the oxidative reaction between it and the molecular halogen to proceed at a reasonable rate.
  • additional elemental phosphorus dissolves, thereby maintaining a continuous supply of dissolved elemental phosphorus available for reaction so long as some undissolved elemental phosphorus remains.
  • non-aqueous solvents which are generally suitable in the practice of the present invention are those which are liquid and inert to elemental phosphorus, molecular halogens, phosphorus trihalides, phosphorous acid, hydrogen halides, and water.
  • liquid it is meant that the solvent is in the liquid state under process temperature conditions.
  • Typical non-aqueous solvents which are suitable for use in the present invention include the aliphatic solvents of the group consisting of liquid alkanes, halogen substituted alkanes, and sulfur substituted alkanes; and the aromatic solvents from the group consisting of benzene and halogen substituted benzenes.
  • An added advantage of these solvents is that they are capable of dissolving the molecular halogen generated during the electrolysis as well as at least sufficient amounts of the elemental phosphorus to permit the oxidative reaction between it and the molecular halogen to proceed at a reasonable rate.
  • Illustrative examples of the foregoing solvents include carbon disulfide, chloroform, carbon tetrachloride, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,1,1,2,2-pentachloroethane, ethyl bromide, butyl chloride, butyl bromide, hexane, octane, benzene, o-dichlorobenzene, 1,2,4-trichlorobenzene, and the like.
  • water-immiscible as used herein means that the solvent and water will form two separate and distinct phases after being mixed together and then allowed to remain quiescent for periods ranging from a few minutes up to about one hour.
  • Elemental phosphorus is a non-metallic element that exists in several allotropic forms (white or yellow, red, and black or violet). All of these forms can be used in the present invention but the white or yellow (the terms are used interchangeably) and red forms are preferred. Of these, the white or yellow form is particularly preferred.
  • the term "elemental phosphorus,” as used herein, designates these allotropic forms.
  • White phosphorus exists as P 4 , having a tetrahedral molecular structure. It is a brittle, waxy solid which has a melting point of 44.1° C. and a boiling point of 280.5° C. Its vapor density corresponds to a formula of P 4 . It is virtually insoluble in water and alcohol, moderately soluble in chloroform, hexane, and benzene, and is very soluble in carbon disulfide.
  • the indirect electrolytic oxidation of the present invention is advantageously carried out by conducting the electrolysis in an electrolysis medium containing elemental phosphorus, an aqueous solution of hydrogen halide, and a non-aqueous solvent which is substantially water-immiscible and capable of dissolving the molecular halogen generated during the electrolysis as well as at least sufficient amounts of the elemental phosphorus to permit the oxidative reaction between it and the molecular halogen to proceed at a reasonable rate.
  • additional elemental phosphorus dissolves, thereby maintaining a continuous supply of dissolved elemental phosphorus available for reaction so long as some undissolved elemental phosphorus remains.
  • the non-aqueous solvent is employed in amounts sufficient to maintain a preferred volume ratio of the aqueous solution of hydrogen halide to the non-aqueous solvent between about 1:1 and about 5:1. It is to be noted, however, that higher or lower volume ratios can be employed without adversely affecting either the efficiency and course of the reaction or the product distribution so long as sufficient amounts of non-aqueous solvent are present to dissolve the molecular halogen generated during the electrolysis as well as at least sufficient amounts of the elemental phosphorus to permit the oxidative reaction between it and the molecular halogen to proceed at a reasonable rate.
  • the electrolysis medium components in a fairly homogenous dispersion, but a true solution is not necessarily required as, for example, elemental phosphorus is only moderately soluble in many of the non-aqueous solvents suitable for use herein and insoluble in water and substantially aqueous solutions. And when a substantially water-immiscible, non-aqueous solvent is employed, it is obvious that it and the aqueous solution of hydrogen halide are substantially mutually insoluble.
  • aqueous phase dispersed relatively uniformly throughout the non-aqueous phase.
  • Such uniform dispersal enables relatively rapid extraction of the molecular halogen produced from the aqueous phase into the non-aqueous phase containing dissolved elemental phosphorus.
  • the preferred relatively uniform dispersion of the two phases facilitates relatively rapid hydrolysis of the phosphorus trihalide to phosphorous acid, with the concurrent extraction thereof into the aqueous phase.
  • the mixing can be carried out in any conventional manner such as by flow mixers, jet mixers, injectors, turbulence mixers, circulating mixer systems, centrifugal pumps, and the like; by paddle and propeller mixers of various designs as well as by turbine or centrifugal impeller mixers, colloid mills, and homogenizers.
  • the present invention may use emulsions as well as true solutions.
  • electrolyses can occur in a solution of the components in one of the phases as, for example, electrolysis of the aqueous solution of hydrogen halide to generate molecular halogen.
  • the concentration of the aqueous solution of hydrogen halide can vary widely, for example, from about 0.5 percent to about 50 percent or more by weight, but preferred concentrations will often be in the range of about 1.0 percent to about 10 percent by weight, or on a molar basis, often in the range of about 0.1 molar to about 3.0 molar. It is to be noted, however, that the concentration of hydrogen halide has little effect on the current efficiencies and product distribution (although there might be a lower limit which would depend on the current density employed).
  • the cell voltage In effecting the present process, the cell voltage must be sufficient to pass the desired current (amperes) and to effect electrolytic oxidation of hydrogen halide. Generally this value should be as close to the theoretical cell voltage as possible, although it is recognized that the cell voltage will vary with electrode materials and their surface conditions, the distance between the electrodes, various materials in the electrolysis medium, resistance of the electrolysis medium, and resistance of cell dividers, when employed. For example, under the conditions employed in the procedural and illustrative Examples described hereinbelow the cell voltage is between about +4.0 volts and about +8.0 volts.
  • the present process can be conducted in the various types of electrolysis cells known in the art.
  • such cells comprise a container made of material capable of resisting action of electrolytes, that is, material which is inert under the reaction conditions, for example, glass or plastic and a cathode and an anode, which are electrically connected to sources of electric current.
  • the anode may be of any electrode material so long as it is relatively inert under the reaction conditions.
  • Suitable anode materials include, for example, graphite, de Noratype dimensionally stable anodes, the precious metals such as platinum, palladium, ruthenium, rhodium, and the like, and the precious metals plated onto other metals, such as, for example, titanium and tantalum, although the precious metal type anodes suffer from the disadvantage of being relatively expensive.
  • the de Nora-type dimensionally stable anodes employ precious metal oxides plated on a titanium substrate.
  • other materials include, for example, ruthenium oxide, mixed with oxides of titanium and tantalum, also plated on a titanium substrate.
  • Dimensionally stable anodes suitable for use in the present process are currently commercially available from the Diamond Shamrock Company, Cleveland, Ohio.
  • the anode materials of choice by analogy with the electrolysis of hydrochloric acid in chlorine cells which involves oxidation of chloride ion at the anode and reduction of hydrogen ions at the cathode, are graphite and de Nora-type dimensionally stable anodes.
  • Graphite functions satisfactorily in the present invention except when an aqueous solution of hydrogen chloride is employed as the source of molecular halogen. In such instances the electrolysis causes significant anode corrosion to occur. It, therefore, becomes advantageous to employ the de Nora-type anodes which are sufficiently stable under the reaction conditions utilized so as to eliminate any corrosion problems.
  • a further advantage resulting from the use of dimensionally stable anodes is the lowering of the halogen overvoltage with a concurrent lowering of energy requirements.
  • any suitable electrode material may be employed as the cathode so long as it is relatively inert under the reaction conditions and does not promote the production of undesirable side products, such as, for example, phosphine in any significant amount.
  • Graphite serves admirably as a satisfactory cathode material, even when an aqueous solution of hydrogen chloride is employed. It, therefore, is the material of choice.
  • Low hydrogen overvoltage metals such as, for example, platinum, palladium, and the like are also suitable as cathode material, although they suffer from the disadvantage of being relatively expensive.
  • High hydrogen overvoltage metallic cathodes such as, for example, mercury, zinc, lead, and the like may be used, but it is advantageous and desirable to avoid their use in that they promote the direct reduction of phosphorus to phosphine.
  • a divided cell may be employed in the practice of the present process, an undivided cell is generally preferred. Such a cell offers marked advantages over divided cells for commercial production purposes in that electrical resistance across a cell-divider is eliminated. It is to be noted, however, that when high hydrogen overvoltage metallic cathodes are employed, divided cells may be preferred so as to avoid reduction of phosphorus to phosphine.
  • the electrolysis cell employed in the procedural Examples herein is primarily for laboratory demonstration purposes. Production cells are usually designed with a view to the economics of the process, and characteristically have large electrode surfaces and short distances between the electrodes.
  • the electrolysis cell utilized in the procedural and illustrative Examples described hereinbelow is shown in FIG. 1 except for four other necks, one of which is used for addition of reactants and periodic sampling. It is stoppered during the electrolysis. The remaining three of the not-shown necks are used for gas-tight attachment of a water-cooled condenser topped with a mercury-sealed gas outlet and vent, a thermometer, and a gas-inlet tube.
  • electrolysis cell 1 comprises a glass reaction vessel consisting of two sections--bottom section 2 and top section 3--joined together at flange joint 4 and secured by fastening means, such as, for example, metal fastening clamps.
  • Cell 1 is equipped with graphite electrodes (or de Nora-type dimensionally stable anode and graphite cathode) 5 which are spaced apart a suitable distance by Teflon rods 6.
  • the Teflon rods (6) are extended to the sides of section 2 of cell 1 to maintain the electrode assembly rigid.
  • Cell 1 is also equipped with a mechanical stirrer which is fitted with a large Teflon paddle (7) capable of effecting vigorous agitation of the reaction mixture.
  • Continuous operations may involve, after product removal, recirculation of the electrolysis medium, or a component thereof, such as, for example, the aqueous solution of hydrogen halide and/or the non-aqueous solvent in a manner similar to that illustrated in FIG. 2.
  • Electrolysis cell 1 is as shown in FIG. 1 except that it contains additional inlets and outlets sufficient to accommodate any desired additions, withdrawals, and recycling of materials. For example, elemental phosphorus is added from reservoir 8 and water is added from reservoir 9.
  • the reaction mixture containing dissolved phosphorous acid flows by line 10 into settling tank 11 where the aqueous phase and the non-aqueous phase are allowed to separate.
  • the non-aqueous layer is removed and recycled to cell 1 by line 12 for repeated use.
  • the aqueous layer flows by line 13 to evaporator 14 where the water and hydrogen halide (aqueous solution of hydrogen halide) are removed by evaporation and recycled by line 15 to cell 1 for repeated use as a source of molecular halogen.
  • the crude phosphorous acid is discharged by line 16 to crystallizer-filter 17 where it is crystallized and filtered by suction filtration. The crystals are removed and collected through line 18, while the filtrate is discharged through line 19.
  • a number of options, including but not limited to those described hereinbelow, are available for utilizing the filtrate discharged through line 19. It can be (a) recycled to cell 1 to facilitate isolation of additional phosphorous acid on a repeated run through the reaction system; (b) transferred to a cell similar to cell 1, with an aqueous solution of hydrogen halide (non-aqueous solvent is not necessary in this cell, but its use is not to be precluded, since its use may prove to have long-term advantages, for example, minimization of anode corrosion) and exhaustively oxidized to phosphoric acid, which is useful as an article of commerce; (c) exhaustively oxidized to phosphoric acid by any other means known to the art, for example, catalytic oxidation; or (d) separated into its component acids by any suitable means known to the art, for example, counter current extraction as described in Kovacs et al, U.S. Pat. No. 3,769,384.
  • the electrolysis of the present process can be conducted at a broad range of temperatures--ambient, or higher or lower temperatures--without any significant effect upon the course of the reaction and the yield of the desired phosphorous acid.
  • temperature ranges from about 20° C. or lower to about 180° C. are satisfactory.
  • volatile materials it may be desirable to avoid elevated temperatures so that the volatile component of the electrolysis medium will not escape, and various cooling means can be used for this purpose.
  • the amount of cooling capacity needed for the desired degree of control will depend upon the cell resistance and the electrical current drawn. If desired, cooling can be effected by permitting a component to reflux through a cooling condenser, or by immersing the electrolysis cell in an ice or ice-salt bath.
  • Pressure can be employed to permit electrolysis at higher temperatures with volatile components, but unnecessary employment of pressure is usually undesirable from an economic standpoint. Moreover, it is to be noted that phosphorous acid, on being subjected to excessive heat, undergoes disproportionation to phosphoric acid and phosphine and/or hydrogen as illustrated in reactions (7) and (8).
  • the preferred temperature is any temperature not sufficient to cause substantial disproportionation. More particularly, the preferred temperature is less than 180° C. and greater than the melting point of the elemental phosphorus utilized because at temperatures greater than 180° C. reactions (7) and (8) occur at a fairly rapid rate and at temperatures greater than the melting point of the elemental phosphorus utilized, any undissolved elemental phosphorus will exist in molten form which facilitates its dispersal throughout the reaction mixture.
  • the process of the present invention involves an indirect electrolytic oxidation reaction and therefore requires a source of oxidizing agent.
  • Aqueous hydrogen halide which is employed in catalytic amounts admirably serves this purpose.
  • the preferred molar ratio range of elemental phosphorus to hydrogen halide present in the aqueous solution is between about 1:1 and about 20:1, although the molar ratio can be considerably higher or lower as desired.
  • any means known to the art such as, for example, employing (a) a greater or lesser volume of the aqueous solution of hydrogen halide having the same concentration; (b) a greater or lesser molar quantity of elemental phosphorus; or (c) some combination of (a) and (b) can be employed to effect a change in the molar ratio of elemental phosphorus to hydrogen halide, a convenient means of effecting such a change is simply to increase or decrease the concentration of the aqueous solution of hydrogen halide. And as noted hereinbefore, the concentration of hydrogen halide has little effect on the current efficiencies and product distribution.
  • the hydrogen halides preferred for use in the present process are hydrogen chloride, hydrogen bromide, and hydrogen iodide. Of these, hydrogen bromide and hydrogen iodide are particularly preferred because of (a) the stability of graphite anodes in their aqueous solutions under process conditions; and (b) the high selectivity towards phosphorous acid which is observed when they are employed. It is recognized, however, that in view of its lower cost, hydrogen chloride might be the hydrogen halide of choice.
  • selectivity is employed herein to mean the percentage of reacting molecules of elemental phosphorus converted to phosphorous acid.
  • the hydrogen halide is electrolytically oxidized to molecular halogen, which in turn oxidatively reacts with elemental phosphorus to form phosphorus trihalide.
  • the thus-formed phosphorus trihalide is hydrolyzed to the desired phosphorous acid and hydrogen halide.
  • the need for external means for disposing of the hydrogen halide generated thereby is eliminated; it is disposed of in situ by recycling by means of electrolytic oxidation to molecular halogen for reuse as a reactant.
  • the halide ions are electrolytically oxidized to regenerate molecular halogen which further reacts with elemental phosphorus to produce additional phosphorus trihalide.
  • the hydrogen ions are electrolytically reduced at the cathode to generate hydrogen gas which, being non-polluting, is safely vented into the atmosphere, or, alternatively, is flared to produce gaseous water as the only product.
  • the phosphorous acid produced in the present invention is conveniently recovered in the form of the free acid.
  • isolation procedures employed in the procedural Examples and discussed herein are primarily for illustrative purposes. Other procedures can be employed, and may be preferred, for commercial purposes.
  • the isolation procedure can be described in the following manner.
  • the aqueous layer is separated in an inert atmosphere and, if desired, analyzed to determine the total yield of phosphorous acid. Utilizing this value and the total amount of elemental phosphorus consumed during the reaction, the percentage yield of phosphorous acid can also be determined.
  • a method suitable for use herein is hydrogen-1 and phosphorus-31 nuclear magnetic resonance spectroscopy which provides a convenient and efficient method of analysis.
  • the aqueous layer is evaporated in vacuo at moderate temperatures to yield a viscous liquid which upon cooling to ambient temperatures partially crystallizes. More complete and more rapid crystallization can be induced by using sub-ambient temperatures and by the addition of a seed crystal of phosphorous acid to the viscous liquid. Filtration of the crystallized mass with prolonged suction under a stream of nitrogen yields phosphorous acid as white crystals. Dissolution of the crystals in water followed by evaporation and filtration in the manner described hereinabove affords white crystals of phosphorous acid.
  • the filtrate from the isolation of phosphorous acid can be recycled to electrolysis cell 1 to facilitate isolation of additional phosphorous acid upon repeating the present process. It can also be utilized by employing any of the remaining available options as described hereinabove.
  • the reaction was carried out in an undivided cell (FIG. 1) comprising a 1-liter glass reaction vessel consisting of two sections--a bottom section and a top section--joined together at the flange joint and secured by fastening means, such as, for example, metal fastening clamps.
  • the top section had seven necks, with standard-taper inner joints, used for gastight attachment of a mechanical stirrer, two platinum wire electrode connections, a thermometer, a water-cooled condenser topped with a mercury sealed gas outlet and vent, and a gas inlet tube. The remaining neck was used for addition of reactants and was stoppered during the electrolysis.
  • the bottom section had a usable volume up to the flange joint of about 800 milliliters.
  • the cell was equipped with graphite-plate electrodes measuring 10 ⁇ 6 ⁇ 1.2 centimeters and spaced 3 centimeters apart by Teflon rods which were extended to the sides of the glass reaction vessel to maintain the electrode assembly rigid. Vigorous agitation of the reaction mixture was accomplished by a mechanical stirrer fitted with a large Teflon paddle.
  • a mixture of white phosphorus (102.0 grams, 3.29 moles), aqueous hydrogen bromide (400 milliliters, 2.4 percent, 0.176 mole; prepared from 20 milliliters of 48 percent aqueous hydrogen bromide and 380 milliliters of water), and chloroform (200 milliliters) was placed in the nitrogen purged cell and heated to about 50° C. under a steady stream of nitrogen. The mixture was vigorously agitated to insure good contact between the now molten white phosphorus and the non-aqueous (chloroform) and aqueous layers. Only a portion of the white phosphorus dissolved initially in the chloroform.
  • the vigorously agitated reaction mixture was thereafter electrolyzed under a steady stream of nitrogen with a constant current of 10 amperes for 25.5 hours (which is equivalent to 255 ampere-hours which equal 9.5 Faradays which equal 2.9 Faradays per mole of white phosphorus).
  • the initial cell voltage of 5.5 volts gradually decreased to 4.5 volts.
  • the passage of current maintained the reaction mixture at reflux (chloroform/water azeotrope--56° C. Upon completion of the reaction, the cell and its contents were allowed to cool to ambient temperatures.
  • the current efficiency for the combined production of phosphorus acids was 91 percent; the conversion of white phosphorus to phosphorus acids as determined by hydrogen-1 and phosphorus-31 nuclear magnetic resonance spectroscopic analysis was 80 percent; and the percentage yield of phosphorous acid isolated was 45 percent based on the conversion of white phosphorus.
  • Example 1 and Examples 2 through 6 using the procedure described in Example 1 above are summarized and tabulated in TABLE 1. Also included in TABLE 1 for comparison purposes are Examples 7 and 8 which were carried out without a non-aqueous solvent.
  • Examples Number 1 through 6 and Examples Number 7 and 8 demonstrates that Examples Number 1 through 6 are significantly more efficient than Examples Number 7 and 8.
  • the average current efficiency for Examples Number 1 through 6 is 86 percent while that of Examples Number 7 and 8 is only 58 percent.
  • Phosphorous acid has a number of useful purposes. It is useful as a reducing agent where a strong but relatively slow-acting reducing agent is desirable. It is also useful as a starting material for the production of phosphitic esters such as diethyl phosphite, which is useful as a lubricant additive, antioxidant, and solvent.
  • Phosphorous acid is also employed as a starting material in the preparation of valuable phosphonate compounds such as ethane-1-hydroxy-1,1-diphosphonic acid which, including water soluble derivatives thereof, are valuable builders for detergent compositions as described in Diehl, U.S. 3,159,581.
  • phosphorous acid is useful in the preparation of various phosphonomethylamines.
  • Such compounds are known agents for various water treating and similar purposes, particularly as scale inhibiting agents as described in Ralston, U.S. Pat. No. 3,336,221, U.S. Pat. No. 3,234,124.
  • such agents are effective in inhibiting corrosion of iron, steel, and other metals coming into contact with such water under highly oxygenated or otherwise possibly corrosive conditions. And, because of their inhibiting, antiprecipitant, chelating, and sequestering properties, such agents are usefully employed in various soaps, detergents, and cleaning compounds.

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US05/640,671 1975-12-15 1975-12-15 Electrolytic preparation of phosphorous acid from elemental phosphorus Expired - Lifetime US4021321A (en)

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Application Number Priority Date Filing Date Title
US05/640,671 US4021321A (en) 1975-12-15 1975-12-15 Electrolytic preparation of phosphorous acid from elemental phosphorus
NL7613752A NL7613752A (nl) 1975-12-15 1976-12-10 Werkwijze voor het indirect elektrolytisch oxyderen van elementaire fosfor.
FR7637670A FR2335619A1 (fr) 1975-12-15 1976-12-14 Procede de preparation electrolytique d'acide phosphoreux a partir de phosphore elementaire et nouveau produit ainsi obtenu
IT30404/76A IT1065412B (it) 1975-12-15 1976-12-14 Procedimento per la preparazione elettrolitica di acido fosforoso da fosforo elementare
GB52017/76A GB1527550A (en) 1975-12-15 1976-12-14 Production of phosphorous acid
JP51149491A JPS5913597B2 (ja) 1975-12-15 1976-12-14 元素状燐の改良された酸化方法
CA267,785A CA1089406A (en) 1975-12-15 1976-12-14 Electrolytic preparation of phosphorous acid from elemental phosphorus
DE19762656593 DE2656593A1 (de) 1975-12-15 1976-12-14 Elektrolytische herstellung von phosphoriger saeure aus elementarem phosphor
BE173283A BE849433A (fr) 1975-12-15 1976-12-15 Procede de preparation electrolytique d'acide phosphoreux a partir de phosphore elementaire et nouveau produit ainsi obtenu

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US4372828A (en) * 1982-02-11 1983-02-08 Koppers Company, Inc. Process for preparing arsenic acid
US4487669A (en) * 1983-01-31 1984-12-11 Koppers Company, Inc. Method for oxidation of an element in both compartments of an electrolytic cell
WO1996020890A1 (en) * 1993-12-20 1996-07-11 Occidental Chemical Corporation Method of making hypophosphorous acid
US6440380B1 (en) 1998-12-15 2002-08-27 Monsanto Technology, Llc Preparation of phosphorus (I) oxides, phosphorus (III) oxides, and lower hydrides of phosphorus by catalytic reduction of phosphorus (V) oxides

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US3437439A (en) * 1967-02-08 1969-04-08 Monsanto Co Preparation of orthophosphorous acid
US3437440A (en) * 1967-02-08 1969-04-08 Monsanto Co Preparation of oxo-acids of phosphorus
US3437438A (en) * 1967-02-08 1969-04-08 Monsanto Co Production of phosphorous acid
US3528772A (en) * 1967-10-26 1970-09-15 Procter & Gamble Process for preparation of orthophosphorous acid
US3532461A (en) * 1966-07-20 1970-10-06 Procter & Gamble Process for preparing chemical compounds containing trivalent phosphorus

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FR1214093A (fr) * 1959-01-23 1960-04-06 Perfectionnements aux machines à tambour horizontal pour laver le linge et autres tissus

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US3532461A (en) * 1966-07-20 1970-10-06 Procter & Gamble Process for preparing chemical compounds containing trivalent phosphorus
US3437439A (en) * 1967-02-08 1969-04-08 Monsanto Co Preparation of orthophosphorous acid
US3437440A (en) * 1967-02-08 1969-04-08 Monsanto Co Preparation of oxo-acids of phosphorus
US3437438A (en) * 1967-02-08 1969-04-08 Monsanto Co Production of phosphorous acid
US3528772A (en) * 1967-10-26 1970-09-15 Procter & Gamble Process for preparation of orthophosphorous acid

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4372828A (en) * 1982-02-11 1983-02-08 Koppers Company, Inc. Process for preparing arsenic acid
US4487669A (en) * 1983-01-31 1984-12-11 Koppers Company, Inc. Method for oxidation of an element in both compartments of an electrolytic cell
WO1996020890A1 (en) * 1993-12-20 1996-07-11 Occidental Chemical Corporation Method of making hypophosphorous acid
US6440380B1 (en) 1998-12-15 2002-08-27 Monsanto Technology, Llc Preparation of phosphorus (I) oxides, phosphorus (III) oxides, and lower hydrides of phosphorus by catalytic reduction of phosphorus (V) oxides

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BE849433A (fr) 1977-06-15
DE2656593A1 (de) 1977-06-16
JPS5913597B2 (ja) 1984-03-30
FR2335619A1 (fr) 1977-07-15
NL7613752A (nl) 1977-06-17
FR2335619B1 (ja) 1979-09-14
CA1089406A (en) 1980-11-11
IT1065412B (it) 1985-02-25
JPS5273199A (en) 1977-06-18
GB1527550A (en) 1978-10-04

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